Frequently Asked Questions
How far away is ‘safe’ from pylons, substations and transformers?
You need to find out what voltage they are and what they are supplying (i.e. residential properties or industrial premises, etc.,) to evaluate the ‘safe’ distance from your property.
Initial guide distances are suggested below; a few lines may need greater clearance, some low-power lines may need less, depending on factors such as how large the load is and whether the load is balanced, which are not always easy to discover.
120 metres from 40OkV & 275kV lines
100 metres from 132kV lines
50 metres from 33kV lines
25 metres from 11kV lines
Remember that the fields come from the cables running between the pylons, not the pylons themselves.
Magnetic fields associated with substations come mainly from the underground cables supplying the power to houses, factories, etc. You will need to find out where the underground cables are in relation to your property, and have the electric and magnetic fields measured- (Your Regional Electricity Company will sometimes offer this service free of charge if you live next to a substation.).
It is important to remember that fields in Winter and/or cold weather can be up to 3 times higher than those measured in warm weather.
In many built up areas the Regional Electricity Companies often connect neutrals from different substations together. The reason they give is to minimise “over-voltage” conditions which might occur if the local neutral became broken.
The disadvantage is that these linked neutrals can cause faulty “net currents” to flow round the system and these can produce high magnetic fields over wide areas (e.g. round 4 or 5 streets).
This is a major cause of elevated domestic magnetic field levels and the only way to discover if it is happening in your area is to measure the magnetic fields at a peak time (say between 5pm and 6.30 pm on weekdays). The fields should be well below 0. 1 microtesla in the summer, and 0.2 microtesla in the middle of winter.
Fields from the substation equipment itself, fall to a ‘safe’ level at approximately 3 metres from the wall of an 11 kV substation, 8 metres from a 33kV substation and more for higher voltage substations (more variable).
These can be found in more rural areas. 4 metres is usually adequate for fields from these transformers to fall to an acceptable level.
How different are the fields between underground and overground cables?
There are two types of fields. Electric fields are there all the time, depending on the voltage of the line. The magnetic field levels depend entirely on the load the cables are carrying at the time of measurement.
The electric fields can be very high. They fall off rapidly with distance and are reduced by buildings and trees, etc. Significant magnetic fields can extend outwards for up to 250 metres from large lines. The fields should be measured. They will not be reduced by anything.
The electric fields are zero as they are screened by earth. The magnetic fields are very high near to the cable (higher than the same distance from overhead cables).
They fall off more rapidly than the fields from overhead wires, and are usually at an acceptable level by 5- 30 metres, unless there are multiple cables carrying a very high load, when the distance for the fields to drop to an acceptable level is more likely to be 50 metres.
How do the different units of measurement compare with each other?
Electric fields are measured in volts per metre (V/m).
In living and especially sleeping areas, you should certainly aim for less than 25 V/m, ideally less than 10 V/m.
Magnetic fields are measured in nanatesla (nT). In living areas and especially sleeping areas, they should be less than 200nT, ideally less than 100nT.
Sometimes magnetic fields are measured in microtesla (μT) or milliGauss (mG). 200nT = 0.2 μT or 2mG.
Magnetic fields can vary considerably during a 24-hour period. Measure them ideally at a peak load time (best is 5pm to 6.30pm weekdays).
Will copper or lead sheeting reduce electromagnetic fields?
Magnetic fields will not be reduced by copper or lead sheeting.
If the sheets are earthed, they will reduce electric fields.
Magnetic fields can only be effectively shielded using high permeability steel sheeting. It is very difficult and expensive to shield large areas such as living or working spaces.
Is it safe for children to play in the garden near lines or cables?
It is not advisable to play near high-voltage overhead lines above 11kV, especially with the new concerns about electric field effects. Evidence suggests that moving about in fields of up to 500nT is unlikely to be hazardous.
What can I do if my fields are high?
High electric fields can usually be significantly reduced, especially inside buildings. High magnetic fields, once created, are almost impossible to reduce. Use the services of a professional EMF consultant. Electricians are not usually fully informed about these problems.
What is a safe distance from a meter cupboard?
Beds and frequently used chairs should be sited at least 2 metres away from electric meters, fuse boxes and the bulk of their associated cables.
This is especially true of anyone who is suffering from an acute or chronic immune-system deficiency.
Watch out for meters mounted on the opposite side of a wall.
Are personal alarms, as used in monitored accommodation. and hearing aids safe?
It is likely that all battery-operated personal alarms and hearing aids are safe.
What do I do about my electronic equipment turning itself on & off
If this is happening frequently, it is likely that you have a source of radio-frequency energy nearby.
There is a humming noise – What is the cause?
The source of a ‘hum’ can be difficult to find.
Hum does not usually come from electrical cables and equipment, although transformers do hum slightly and, if faulty, can hum loudly.
Ask others if they can hear the hum, not just the people living in the same house as yourself.
A common source of hum is road noise, from major roads up to 1 mile away, resonating in bedrooms. It can usually be cured by thick curtains and other sound absorbent materials.
Another source of Low Frequency Noise comes from long distance major gas pipe lines which are pressurised by large engines. This sound can travel several miles through the ground and only some people can sense it. It does not show up on normal noise level meters, specialised equipment is necessary.
What can I do if I am being ‘zapped’ by my neighbours?
It is very difficult to eliminate EMR, while the technostress from EMF can be reduced. Talk to you neighbours about the possible sources of the technostress. If you feel you are being ‘zapped’, it imay be that you have developed electrical or chemical hypersensitivity.
How do you measure microwaves?
Microwaves from communications systems e.g. mobile phones, need very complex equipment to measure them meaningfully. Signals pulse on and off in a manner that makes simple measurements totally inadequate.
Are mobile phones dangerous? What about cordless phones?
There is now good evidnecce that the use of mobile phone pose a health risk. This is especially so for children and anyone with prolonged use. It is best to use the speaker option, or a headset, so the phone can be held further from your head.
The old fashioned type phone – Simple analogue-type cordless phones are not likely to be hazardous.
Digital cordless phones (DECT) are the same technology as mobile phones and therefore be less safe.People report severe headaches and other problems from the use of DECT phones.
What about personal radios used by the A.A., RAC, Police, Taxi-drivers etc.?
These are usually higher powered than mobile phones. It is not recommended that you use hand-held sets without extending the aerial (if possible), and avoid using them inside a vehicle.
Does the risk increase the more I am exposed to fields?
The evidence is that damage from electromagnetic fields is both instantaneous and cumulative.
What electrical appliances give off high fields and what can I do about them?
It must be remembered that all items connected to the mains electricity supply will give off both electric and magnetic fields.
They may also give off radio-frequency and microwave radiation.
Any appliance which only has a two wire mains lead (i.e. Neutral (blue) & Line (brown)) and no ‘Earth’ connection (green/yellow) will almost always give off high electric fields. Most battery/mains appliances only have two-wire connections, and also usually contain a cheap transformer which ‘leaks’ high levels of magnetic fields even when the appliance is switched off at its internal switch. Such appliances need to be switched off at the wall, or unplugged, to remove the fields.
See also this rough guide to Dangers of Techno-stress